[E34] M60B30 3.0 Optimal air intake.

[632 Regal]

Frank, I have been trying to follow several people trying the 4.0 intake parts on the 3.0 with ZERO followup. Only reason I can think of is due to negative results. I am not dogging the idea at all because I have access to all 4.0 parts 3 feet from my tools. I am definitely a believer in the bigger is better theory even though real life has beat me up on that idea many many times.

My 3.0 picked up a bit of low end by timing the cams although I advanced it about 4-6 degrees, technically I retarded one of the cams so it is still wrong but a bit better. Got my 60-80 times to 5 seconds avg. so I am back in the ballpark.

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Theory behind bigger vs smaller in acceleration.

The 3.0 has high duration high overlap camshafts which are made for higher RPM's. My experience with these 3.0s is they don't like much less than 3500 RPM's.
The 4.0 has the same size and duration cams but the valves are larger to make up for the difference in engine size. (No personal experience with the 4.0 RPM's)

The cam duration lowers compression pressures allowing it to run 10.5 without serious detonation at lower RPM's. (10:1 with the 4.0)

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My experience with higher output engines in general. Based on 2 valve engines for street or race, basically as much HP as I could get out of them.

Cams - Bigger cams are good but limiting factor is RPM. When it starts turning power and max rpm the engine will run.
The 3.0 is great above 3500 RPM's which is a high RPM for the conventional 2 valve engines I worked with. So lets consider these already have huge cams which they do in reality.

Let's throw on a bigger carburetor, stock intake manifold. (IE bigger throttle body / intake system same manifold). Low end may be the same but most likely worse until after that 3500 RPM area where the engine (cams) start working. Possible a stronger higher upper RPM.

Using the above lets pop that huge runner intake manifold on it. Going to lose volumetric efficiency big time. Perhaps it wont be turning on until 4K RPM. Might have more power above 5-6K RPM.

Big Manifold with small intake throttle body and tube most likely a loss in low RPM's through high rpms. The way an intake manifold tube works is the speed which the air travels through there. Smaller tube will have a higher speed which will build up under the intake valve prior to it opening. Kinda like a charge of pressure. Think super charger or turbo. Neither will give any power below the turn on point of the engine/cam combination. With a bigger manifold tube you will never get the air speed as a smaller intake tube. So in theory of bigger intake it shouldn't help unless it is a bottleneck such as above 7500 RPM and up.

The idea of more power is limited to where you want the power. Do you want low, mid or high RPM increases. I wish I has personal experience with the 4.0. I don't know what RPM's they turn on. I only have that with the 3.0.

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My experience would say smaller plenum intake would help lower RPM's and larger would help with higher. But again this all depends on RPM's and VE (volumetric efficiency).

Just my opinion here.

3.0 would not benefit with any larger anything, possible high rpm benefit with larger throttle body and intake tube. We (3.0) are already over carb'd (Big throttle body and cams) and intake runners until 3500 rpm's. Increasing any intake sizes should make zero benefit either way or rpm.

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Edit in case my PC crashes.

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Ideas with the 4.0

If torque is lagging below 3500 RPM's replace the intake with the 3.0 intake
but keep the throttle body and intake tubes 4.0 for higher rpm's.
The runner efficiency should benefit it all until about 5000-6000 rpms and then be a possible bottle neck.
Would not negatively effect the lower rpms at all as much as it will the 3.0 but possible high rpm will be lower Possibly not, small thing to compare at this point though..

Should cause a lower rpm torque monster. But not a highway monster.

It's all a give and take as I wrote. I hope this helps because I am very interested.